use strict;
use warnings;
use feature         qw( state );
use Benchmark       qw( cmpthese );
use List::Util      qw( first shuffle );
use List::MoreUtils qw( firstidx indexes );

my @array = shuffle (1 .. 1e6);

cmpthese
(
    10,
    {
        grep     => sub { _grep()     },
        first    => sub { _first()    },
        indexes  => sub { _indexes()  },
        firstidx => sub { _firstidx() },
    }
);

sub _grep
{
    state $init = 1;

    my ($i1) = grep { $array[$_] == 1 } 0 .. $#array;
    my ($i2) = grep { $array[$_] == 2 } 0 .. $#array;
    my ($i3) = grep { $array[$_] == 3 } 0 .. $#array;

    if ($init)
    {
        printf "<%d> <%d> <%d>\n", $i1, $i2, $i3;
        $init = 0;
    }
}

sub _first
{
    state $init = 1;

    my $i1 = first { $array[$_] == 1 } (0 .. $#array);
    my $i2 = first { $array[$_] == 2 } (0 .. $#array);
    my $i3 = first { $array[$_] == 3 } (0 .. $#array);

    if ($init)
    {
        printf "<%d> <%d> <%d>\n", $i1, $i2, $i3;
        $init = 0;
    }
}

sub _indexes
{
    state $init = 1;

    my $i1 = indexes { $array[$_] == 1 } (0 .. $#array);
    my $i2 = indexes { $array[$_] == 2 } (0 .. $#array);
    my $i3 = indexes { $array[$_] == 3 } (0 .. $#array);

    if ($init)
    {
        printf "<%d> <%d> <%d>\n", $i1, $i2, $i3;
        $init = 0;
    }
}

sub _firstidx
{
    state $init = 1;

    my $i1 = firstidx { $_ == 1 } @array;
    my $i2 = firstidx { $_ == 2 } @array;
    my $i3 = firstidx { $_ == 3 } @array;

    if ($init)
    {
        printf "<%d> <%d> <%d>\n", $i1, $i2, $i3;
        $init = 0;
    }
}
[download]

Output:

23:20 >perl 1940_SoPW.pl
<748548> <843435> <178789>
<748548> <843435> <178789>
<748548> <843435> <178789>
<748548> <843435> <178789>
           Rate     grep  indexes    first firstidx
grep     1.19/s       --      -1%     -34%     -52%
indexes  1.20/s       1%       --     -34%     -51%
first    1.81/s      53%      51%       --     -27%
firstidx 2.47/s     108%     106%      37%       --

23:20 >
[download]